1. Field of the Invention
The present invention relates to electrical contacts, more particularly, to apparatuses for attaching electrical terminals to wire conductors.
2. Description of the Related Art
Electrical terminals are used to terminate the conductor(s) of electrical wires and cables. The typical electrical terminal has a contact portion and a crimp portion for attaching the wire conductor. The crimp portion can be cylindrical, known in the industry as “closed barrel”, or “U”-shaped, known as “open barrel.” Typically, the wire or cable is stripped of its jacket or insulation to expose the conductor, the conductor is inserted into the crimp portion, and the terminal is crimped to the conductor to form a mechanical bond between the conductor and the terminal. This bond must be solid to ensure integrity and robustness.
The use of mechanical devices to attach electric terminals to wire is well-known in the industry. Electrical terminals have been crimped to wire, either manually, semi-automatically, or automatically, in close tolerance machinery such as applicators and presses. The applicator precisely positions the terminal at a location where the tooling portion of the applicator can squeeze the crimp portion around the wire conductor to form a crimped bond. A press supplies the force and motion needed by the applicator to repeat this cycle many times.
An applicator 14 of the prior art is shown in FIG. 1. The applicator 14 includes a metal frame 1, a plunger or ram 2, a crimp punch 3, an anvil 4, guides 5, a brake 6, a base plate 7, plunger caps 10, a terminal advancing mechanism or feeder mechanism 8, a feeder adjustment 15, and a crimp height adjustment mechanism 9. The applicator 14 is used in conjunction with a press, not shown. The press provides motion and force for the applicator to advance, fixture, and compress a terminal's crimping portion securing it to the wire conductor.
It is common to produce applicator components, including the applicator frame, from metals of various types. These metals can be ferrous or non-ferrous, in block or cast form, and may be iron, steel, aluminum, bronze, or other metals and/or alloys. A strong material is needed to provide a solid platform and guide to which most of the applicator's components are attached or interfaced.
Machining a frame from a block of metal or casting a frame with a form can provide a solid foundation but there are many shortcomings inherent to the use of metals and the production methods used to produce metal frames. Complex geometries machined to close tolerances are needed for a quality finished product. As shown in FIG. 2, milling used at 17, drilling used at 18, tapping used at 19, grinding used at 20, reaming used at 21, and de-burring used at 22, are some of the procedures used to manufacture a metal frame. Electrical discharge machine (EDM) used at 23 is another subtractive manufacturing process used to remove raw material in the construction of a metal frame. These methods require special tools, handling, fixturing, and time, and must be repeated for each frame. Consequently, the turnaround time to order and receive a new or replacement applicator can be several weeks.
Iron, aluminum, steel and most feasible alloys are subject to some form of corrosion. Finished metal frames are typically painted or coated, and these processes require additional steps such as cleaning, degreasing and masking.
Additionally, the price of the metals and the perishable tooling can greatly add to the cost of the frame.
Applicator frames made of steel or iron are heavy. Ergonomic issues like the weight of the applicator and its location in the press can make set-ups and re-sets of the applicator cumbersome and time-consuming.
During operation, the feeder 8 positions the terminal 13 above the anvil 4. After the conductor 12 is inserted into the crimp portion, the press pushes the plunger 2 downwardly. This action brings the crimp punch 3 into contact with the crimp portion, compressing it against the anvil 4, thereby forming the terminal-to-wire crimp bond. The effectiveness of the crimp is dependent on the integrity of the frame 1 and its ability to rigidly guide and maintain the precise location of the applicator components and mechanisms for many cycles.
Frames of metal construction are not efficiently designed to dissipate heat. Consequently, after several hours of cycling, the temperature of the applicator frame can rise. This thermal instability affects the fixture's ability to hold dimensional tolerances of the finished crimp, leading to the need to make adjustments to the equipment. However, the heat can also make the equipment uncomfortably hot to the touch for the technician making the adjustments, inviting potential safety concerns.
There exist in the industry needs for improvements to the applicator in order to improve the overall efficiency of the automated and semi-automated crimping process.